1. Technical Field
This invention relates generally to passive optical networks, and more particularly to data transmission and reception systems and methods for passive optical networks.
2. Background Art
Passive optical networks transmit large amounts of data using optical fibers. In passive optical network systems, un-powered optical splitters allow a single fiber to serve multiple end units, which are commonly referred to as optical network units or optical network terminals. Optical network units are end units configured, typically, to serve multiple users. For example, an optical network unit may serve the occupants of an apartment building. Optical network terminals are end units serving a single user, such as a residence or business.
An optical line terminal is disposed at one end of the passive optical network, with the end unit disposed at the other. The optical line terminal, frequently part of a communication service provider's hardware, is a device that receives electrical signals from service providers, converts those signals to optical signals, and then transmits the optical signals to end units across the optical data network. In traditional passive optical network systems, the optical line terminal delivers a single downstream signal that is received by every end unit. Said differently, each optical network unit or optical network terminal sees the same downstream signal, with data designated for the optical network unit or optical network terminal forming only a portion of the downstream signal. Encryption of packets in the downstream signal prevents one end unit from eavesdropping on the other. Upstream data from the end units is then multiplexed in accordance with a known standard.
While traditional passive optical networks work well in practice, the amount of data that can be transmitted is constrained. The data transmission rate or bandwidth is constrained both by the fact that a common downstream signal must be shared by multiple users and by the physical cost required to increase transmission rates. Small increases in data transmission rates can require an exponential increase in cost. It would be advantageous to have methods and systems suitable for passive optical networks that can increase data transmission rates without significantly increasing cost.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.